Down-hole tools

Abstract

A time delay mechanism wherein there is provided a time delay between the application of a pressure to the mechanism and an action being carried out as a result of the application of said pressure. The mechanism may comprise a first piston and piston chamber and a second piston and piston chamber. Communication of a viscous fluid between said piston chambers may be achieved by means of at least one contoured flow passage.

What is claimed is: 
     
       1. A time delay device for use with a down-hole tool, the time delay device comprising: a first chamber communicable with a second chamber via at least one restrictor;   means for controllably transporting a fluid from said first chamber to said second chamber; and   a one-way check valve provided between the first chamber and the second chamber, wherein the one-way check valve allows fluid to flow from the second chamber to the first chamber at a flow rate greater than the flow rate of the fluid through the at least one restrictor.   
     
     
       2. The time delay device of claim 1, wherein the transport means comprises a first piston. 
     
     
       3. The time delay device of claim 2, wherein said second chamber provides a second piston. 
     
     
       4. The time delay mechanism of claim 3, wherein the second piston is movable via applied pressure from a first position to a second position under the influence of movement of the first piston against the influence of biasing means within the second chamber. 
     
     
       5. The time delay mechanism of claim 3, wherein the at least one restrictor between the first and second chambers is a Lee visco jet. 
     
     
       6. The time delay mechanism of claim 3, wherein the flow rate of fluid through the at least one restrictor, and hence the time delay between the application of pressure to the first piston and action of the second piston, may be varied by changing the flow characteristics of the at least one restrictor. 
     
     
       7. The time delay mechanism of claim 1, wherein the first and second chambers are filled with a fluid. 
     
     
       8. The time delay mechanism of claim 7, wherein the fluid is silicone. 
     
     
       9. A down-hole tool including a time delay device, the time delay device comprising: a first chamber communicable with a second chamber via at least one restrictor;   means for controllably transporting a fluid from said first chamber to said second chamber; and   a one-way check valve provided between the first chamber and the second chamber, wherein the one-way check valve allows fluid to flow from the second chamber to the first chamber at a flow rate greater than the flow rate of the fluid through the at least one restrictor.   
     
     
       10. A method of providing a time delay for a down-hole tool between the application of pressure and an action being carried out as a result of said application of pressure, comprising the steps of: providing a first chamber having a fluid;   providing a second chamber communicable with said first chamber via at least one orifice;   controllably transporting said fluid from said first chamber through said at least one orifice to said second chamber in response to pressure applied to the down-hole tool; and   providing a one-way check valve between the first chamber and the second chamber to allow fluid to flow from the second chamber to the first chamber at a flow rate greater than the flow rate of the fluid through the at least one orifice.   
     
     
       11. A down-hole pressure equalizing device comprising a body having at least one closing port and openable closure means for closing the at least one port wherein, in use, the openable closure means are controllably opened by means of a time delay mechanism, the time delay mechanism comprising a first chamber communicable with a second chamber via at least one restrictor and means for controllably transporting a fluid from the first chamber to the second chamber, wherein a one-way check valve is provided between the second chamber and the first chamber to allow fluid to flow from the second chamber to the first chamber at a flow rate greater than the flow rate of the fluid through the at least one restrictor. 
     
     
       12. The device of claim 11, wherein the time delay mechanism comprises a first piston and a first piston chamber, the first piston chamber being communicable with a second piston and a second piston chamber via at least one restrictor. 
     
     
       13. The device of claim 12, wherein the second piston is movable from a first position to a second position under the influence of movement of the first piston against the influence of biasing means within the second chamber. 
     
     
       14. The device of claim 13, wherein movement of the second piston to the second position allows the openable closure means to open, thereby equalizing pressure across the device. 
     
     
       15. The device of claim 12, wherein the first and second piston chambers are filled with a fluid. 
     
     
       16. The device of claim 15, wherein the fluid is silicone. 
     
     
       17. The device of claim 12, wherein a one-way valve is provided between the second chamber and the first chamber to allow fluid flow from the second chamber to the first chamber. 
     
     
       18. The device of claim 11, wherein the device has connection means provided at or near an uppermost portion thereof for suspending the device from another device. 
     
     
       19. The device of claim 11, wherein the body is a cylindrical housing having a plurality of ports spaced around the circumference thereof, and the openable closure means is a mandrel within the housing moveable therealong. 
     
     
       20. A method of controlling pressure down-hole by providing a down-hole pressure equalizing device comprising a body having at least one port and openable closure means for closing the at least one port, the method comprising controllably opening the openable closure means by means of a time delay mechanism, the time delay mechanism comprising a first chamber communicable with a second chamber via at least one restrictor and means for controllably transporting a fluid from the first chamber to the second chamber, wherein a one-way check valve is provided between the second chamber and the first chamber to allow fluid to flow from the second chamber to the first chamber at a flow rate greater than the flow rate through the at least one restrictor.